Five moments when the prime minister could have discovered that Andy Coulson was not telling the truth about phone hacking at the News of the World:

• After the jailing of his royal editor, Clive Goodman, in January 2007, Coulson consistently claimed that Goodman was 'a rogue reporter' – the only person at the News of the World who had been involved in the activities of the specialist phone-hacker, Glenn Mulcaire, who was jailed at the same time. Both men were sentenced for intercepting the voicemail of three palace staff. Mulcaire alone was also sentenced for hacking five non-royal targets.

• In March 2007, when George Osborne and David Cameron first discussed hiring Coulson, they could have obtained the transcript of the sentencing hearing in January – a public document, available on request. This would have revealed that the judge, Mr Justice Gross, having examined the prosecution evidence in full, concluded that in relation to his five non-royal targets, Mulcaire "had not dealt with Goodman but with others at News International" – a straightforward contradiction of Andy Coulson's 'rogue reporter' claim.

• In July 2009, the Guardian published its first hacking story and then provided evidence to the House of Commons media select committee. This included giving the committee what became known as "the email for Neville", which showed that a junior reporter at the News of the World had emailed Mulcaire the transcripts of 35 voicemail messages which Mulcaire had taped from the phone of Gordon Taylor, the chief executive of the Professional Footballers Association. In the email, the junior reporter asked Mulcaire to pass the transcripts to the paper's chief reporter, Neville Thurlbeck. The message clearly implied that both the junior reporter and Thurlbeck were aware of Mulcaire's activity. Thurlbeck has since pleaded guilty to conspiring to intercept communications.

• In February 2010, the media select committee published a thick volume of evidence including the email for Neville, other documents and oral testimony from News International, the police and Andy Coulson. On the basis of this evidence, the cross-party committee, which was chaired by Conservative MP John Whittingdale, concluded that there was no direct evidence that Coulson had been involved in hacking but – crucially – that it was 'inconceivable' that Goodman had acted alone. They also criticised the failure to uncover the truth by Scotland Yard and the Press Complaints Commission, whose conclusions Cameron nevertheless continued to cite in defence of Coulson.

• Also in February 2010, the Guardian published a detailed account of four private investigators who had a history of criminal activity and who had worked for the News of the World while Andy Coulson was either deputy editor or editor. This included the disclosure that one investigator – who could not and can not be named for legal reasons – had been involved in particularly serious criminal offences on behalf of the newspaper and had then been jailed for seven year for a separate offence and, following his release from prison, had been rehired by Coulson's paper in spite of his criminal record. Following the story, the Guardian's editor relayed his concern about Coulson to Nick Clegg, who was to become Cameron's deputy prime minister in May 2010; and the then deputy editor, Ian Katz, relayed the same warning to Cameron's director of strategy, Steve Hilton, and to his chief of staff, Ed Llewellyn.

• In September 2010, the New York Times published the results of its own investigation, which repeated the Guardian's disclosures of the scale of phone-hacking under Coulson's editorship and added on-the-record comments from one of Coulson's former journalists, Sean Hoare, who said that he had played intercepted voicemail to Coulson, who had actively encouraged him to hack phones. Hoare repeated his claims on BBC radio.